Dupont-Aignan was criticized by Jewish officials in France for his harsh criticism of Israel at the onset of ground operations during Operation Protective Edge.
At the time, Dupont-Aignan's comments were contrary to the position of French President Francois Hollande, who gave Israel some breathing room during the operation in Gaza.
In comments sharply attacking the Israeli government and Western nations for giving Israel the green light to conduct the operation, Dupont-Aignan said, "After the bombings and enormous damage in the killing of hundreds of innocent civilians, men, woman and children, the Israeli-Palestinian conflict has entered a new phase with the Israeli army's invasion of the Gaza Strip, while the UN, West and France remain silent."
At the time, Dupont-Aignan stressed the "lack of proportionality" between the combined forces involved in fighting in the Gaza Strip.
"Whatever responsibility Hamas leaders have in the break out of this conflict, the path Israel has chosen will only lead to a dead end. The tension and hatred in the region against Netanyahu will not be reduced by piles of rubble and corpses. France's attitude towards it is absolutely scandalous," said Dupont-Aignan.
In a statement to French President Francois Hollande during the operation, Dupont-Aignan said, "We expect our government to take the initiative for international action that will force Israel to respect UN resolutions, meaning, to withdraw from the territories and dismantle the illegal settlements.
"Only in this way will it be possible to avoid importing this conflict into our country and to stop the new massacre being waged. Only thus will it be possible to restore lasting peace to the Middle East. If we allow this intolerable situation to worsen and worsen, it will be an act that is not only stupid, but also criminal."
Dupont-Aignan did not only reserve controversial statements on the Israeli-Palestinian conflict for Operation Protective Edge.
During a contentious vote in the French Parliament on recognizing a Palestinian state, he said, "For more than 100 years, Palestine has been in dispute between two peoples whose legitimacy is the same," he wrote.
"Some of the Israeli and Palestinian leaders are responsible together for the impasse," Dupont-Aignan added, referring to Netanyahu on one hand and Hamas on the other.
"I will vote for the establishment of a Palestinian state because it is the only way to solve this conflict that has poisoned the Middle East and the world for decades, a logical act that many Israelis support despite the terror attacks, the rocket threat and the suicide bombings."
Le Pen's announcement aims to secure the nearly 1.7 million votes that the anti-European Union conservative got when he was eliminated from the race in the first round of balloting.
Since many Dupont-Aignan voters had already been expected to switch to Le Pen for her second-round duel against the centrist Macron, his decision to ally himself with her was unlikely to prove a massive electoral boost for her campaign.
Reuters contributed to this report.